During metal stamping, a sheet of metal is positioned over a die opening or die cavity before a punch is rapidly pushed through the sheet into the die opening or cavity of cutting a blank or slug from the sheet having substantially the same shape or contour as the profile of the die cavity. Particularly, where the blank or slug is intended to be pushed through the die cavity, retraction of the punch can cause the blank or slug to undesirably pull out of the die.
To prevent circular blanks or slugs from pulling out of the die, Kramski, U.S. Pat. No. 4,543,865, discloses machining a small groove into part of the sidewall defining the die cavity that provides interference by causing part of the blank or slug formed during stamping to expand into the groove. As a result of the blank or slug expanding into the groove during stamping, pressure between the blank or slug and die land occurs preventing the blank or slug from pulling back through the top of the die and onto the work zone.
What is needed is a machine and method for machining one or more slug keeping grooves or slug retention grooves in a die. What is also needed is a machine and method usable in the field to machine one or more slug keeping/retention grooves in a die without having to remove the die from the stamping press.